Mutants of Saccharomyces cerevisiae were isolated which have decreased ability to hydrolyze leucine P-naphthylamide, a chromogenic substrate for aminopeptidases. The mutations were shown by starch gel electrophoresis to affect one offour different aminopeptidases. Mutations affecting a given enzyme belong to a single complementation group. The four genes were symbolized lap), lap2, lap3, and lap4, and the corresponding enzymes LAPI, LAPII, LAPIII, and LAPIV. Both lap) and la$ were mapped to the left arm of chromosome XI, and lap3 was mapped to the left arm of chromosome XIV. Strains which possessed only one of the four leucine aminopeptidases (LAPs) were constructed. Crude extracts from these strains were used to study the properties of the individual enzymes. Dialysis against EDTA greatly reduced the activity of all the LAPs except for LAPIII. Of the cations tested, Co2+ was the most effective in restoring activity. LAPIV was the only LAP reactivated by Zn2+. LAPI was purified 331-fold and LAPII was purified 126-fold from cell homogenates. Both of the purified enzymes had strong activity on dipeptides and tripeptides. The activity levels of the LAPs are strongly dependent on growth stage in batch culture, with the highest levels in earlystationary phase. Strains lacking all four LAPs have slightly lower growth rates than wild-type strains. The ability of leucine auxotrophs to grow on dipeptides and tripeptides containing leucine is not impaired in strains lacking all four LAPs.The proteolytic system of Saccharomyces cerevisiae has been actively investigated over the past decade. The functions presumably carried out by proteases and peptidases in S. cerevisiae include hydrolysis of peptides to provide amino acids (18), intracellular protein turnover (12), and specific proteolytic cleavages, such as catabolite inactivation (11), activation of chitin synthetase (8), and hydrolysis of the alpha factor by a mating type cells (6). Two endoproteases, proteinases A and B, and two carboxypeptidases, Y and S, have been identified in S. cerevisiae (24). Two aminopeptidases, aminopeptidase I (20) and aminopeptidase II (9), and a dipeptidase (26) have been purified and characterized. Matile et al. (19) detected four aminopeptidases with activity on leucine 3-naphthlyamide (LBNA) after separating crude extracts from yeast by starch gel electrophoresis. Four aminopeptidases capable of hydrolyzing tripeptides were detected by Rose et al. (27) on polyacrylamide gels. However, the relationship among the aminopeptidases t Present address

The novel design of a heated stage ͑miniature dye bath͒ for use with an inverted fluorescence microscope is described. The heated stage allows investigation of wool dyeings to be followed in situ in real time. The photometer attachment of the microscope allows for quantitative analysis. The progress of the dyeing of wool with a fluorescent whitening agent and a fluorescent dye have been monitored in real time.

Hyperon decays present a promising alternative for extracting |𝑉 𝑢𝑠 | from lattice QCD combined with experimental measurements. Currently |𝑉 𝑢𝑠 | is determined from the kaon decay widths and a lattice calculation of the associated form factor. In this proceeding, I will present preliminary work on a lattice determination of the hyperon mass spectrum. I will additionally summarize future goals in which we will calculate the hyperon transition matrix elements, which will provide an alternative means for accessing |𝑉 𝑢𝑠 |. This work is based on a particular formulation of SU(2) chiral perturbation theory for hyperons; determining the extent to which this effective field theory converges is instrumental in understanding the limits of its predictive power, especially since some hyperonic observables are difficult to calculate near the physical pion mass (e.g., hyperonto-nucleon form factors), and thus the use of heavier than physical pion masses is likely to yield more precise results when combined with extrapolations to the physical point.

Hyperon decays present a promising alternative for extracting |𝑉 𝑢𝑠 | from lattice QCD combined with experimental measurements. Currently |𝑉 𝑢𝑠 | is determined from the kaon decay widths and a lattice calculation of the associated form factor. In this proceeding, I will present preliminary work on a lattice determination of the hyperon mass spectrum. I will additionally summarize future goals in which we will calculate the hyperon transition matrix elements, which will provide an alternative means for accessing |𝑉 𝑢𝑠 |. This work is based on a particular formulation of SU(2) chiral perturbation theory for hyperons; determining the extent to which this effective field theory converges is instrumental in understanding the limits of its predictive power, especially since some hyperonic observables are difficult to calculate near the physical pion mass (e.g., hyperonto-nucleon form factors), and thus the use of heavier than physical pion masses is likely to yield more precise results when combined with extrapolations to the physical point.